1. Field of the Invention
The present invention relates to television signal processing and, more particularly, to processing of auxiliary data contained in a digital television signal.
2. Background Information
Most television signal processing systems in the United States provide for the processing of auxiliary information such as closed caption (CC) data that is carried in analog television signals (e.g. NTSC). Auxiliary information such as closed caption data follows EIA-608 which establishes the standard for providing auxiliary data in analog television signals. Analog television signal processing systems extract the closed caption data from the analog television signal and generate a signal suitable for displaying the closed caption information. Other forms of auxiliary information also exist. For example, Extended Data Services (XDS) information may be included in an analog television signal for providing information such as program content rating data, program title, program duration, etc.
With respect to digital television signals (e.g. ATSC), EIA-708 establishes the standard for providing auxiliary data such as closed caption (CC) data and XDS data in digital television signals. However, with the transition from analog programming (i.e. analog television signals) to digital programming (i.e. digital television signals), television signal service providers cannot always provide digital closed caption data in the digital programming. Because of this, television signal providers may transfer the analog closed caption data to the digital programming. To support this transfer of analog closed caption data on digital programming, digital television signal service providers simply embed the analog closed caption data into the digital television program stream with specific headers. Since EIA-708B describes how to detect embedded EIA-608 closed caption data in a digital television stream, it is possible to detect and display analog closed caption data (i.e. EIA-608 CC data) from the digital television stream.
Some televisions provide a user with an option to select either digital or analog captioning for display. If the user selects analog captioning and no analog captioning is available, the television will not display any closed caption. As well, if the user selects digital captioning and no digital captioning is available, the television will not display any closed captioning. Currently, however, there is no manner of always displaying closed caption data for a digital television channel regardless of whether the closed caption data is in analog or digital form.
It is thus evident from the above discussion that what is needed is a television signal processing system for digital television signals that detects whether digital or analog auxiliary data is available in the digital television signal and then processes for display whichever auxiliary data format is available.
These needs and others are accomplished through application of the principles of the subject invention and/or as embodied in one or more various forms and/or structures such as are shown and/or described herein.